Electro-dynamic microphone



Nov. 3, 1936. c. R. HANNA- ELECTRO-DYNAMIC MICROPHONE Original FiledAug. 25, 1925 I!!! llll- In Illlll\ \S INVENTOR Clz'nfon R Hanna.

BY fl/ WITNESSES:

A ORN'EY ReiaanedNov.3,l936

PATENT OFFICE BIECTBO-DYNAHIC MICROPHONE Original No. 1,792,300, datedFebruary 10, 1931, 8th] 5, m5. Renewed No. m, July 1'], 1m

scam

This invention relates to signal translating devices, particularly tomicrophones or similar devices intended to translate sound into electriccurrentorperiodiecurrmttosound.

5 My invention is principally intended for application to signaltranslating devices which do notemployahornandoertainaspeetsof theinvention are of more value in connection with microphones that withtelephone receivers.

10 It is an object oi my invention to provide a microphone in which thediaphragm shall be shielded effectively from all sounds except thosedirected toward it from mrtain angles.

It k a further object of my invention to pro- 15videsuchshieldingmeanssoarrangedthatitshallnotcausematerialrestoringforcesuponthe diaphragm.

This result involves providing a passage from the shielded side of thediaphragm to the open 20 air through which air pressures may be relievedbut in which sound waves are attenuated. The means for attenuating thesound waves in said passage tend also to prevent resonance within theshielding device.

25 The mponse of the signal translating device at different frequenciesshould either be uniform orvaryaceordingtoasimplelaw,wherebythevariations may be compensated by suitablydesigningthecircuitwithwhichthedeviceiscon- 30 nected.Ifthevibratingsystemposessesanatggaa g August Application 80. 1932.Serial No. 628,434

for rel-us July.

ticularly useful when it is mechanicallyconnectedtoacoilmovinginanairgapandhaving small clearance.

I provide a flexible member for connecting the small end of the cone toits support, which memher can be made out of sheet material by punchingor similar operation, shall be small enough to re'adib be includedwithin the small end of the cone and flexible enough to avoid inducingundesired effects upon the vibrating system. It is also contemplatedthat the support for the small end of the cone shall be at the center ofone pole piece of the magnetic circuit.

Other objects of my invention and details of the structure will be clearfrom the following description and the accompanying drawing, in whichFig. 1 is a view, in longitudinal section, of a microphone embodying myinvention,

Fig. 2 is a section upon the line II-II of Fig. 1.

Fig. 3 is a section, upon a larger scale, of the diaphragm and coil, and

Fig. 4 is a plan, upon a still larger scale, of the flexible supportingmember for the small end of the diaphragm.

The translating device includes a magnet, which may be either apermanent magnet or an electromflsnet. The magnet shown comprises acentral core I, a winding 2 and an enclosing cup or shell3,whichissecuredtothecore I.

At the other end a cover 4 is provided having good magnetic connectionto the shell 3.

The cover 4 has a central opening 5 into which extends the reduced end 6of the central core I. The cover I and the reduced end 6 thus constitutepole pieces for the magnetic circuit and the space between themconstitutes an annular air gap. The surfaces adjacent tov the air gapmay be plated with conducting material as indicated at I and 8. 40

For example, the surfaces may be copper plated. The purpose of thisplating is explained in my copending application, Serial No. 52,268,filed August 25, 1925, now Patent No. 1,691,243 of November 13, 1928.and assigned to the Westinghouse Electric 8: Manufacturing Company.

The magnet is surrounded by a casing ll sup ported from the shell 3 bybrackets l2 and it. One end of the casing has an opening it, preferablysupplied with'a screen IS. The brackets I! at the other end of thecasing support a collar It to which is secured by cementing, clamping orin any other suitable manner, an annular piece 11 of flexible material,such as kid. The casing II has an opening ll adjacent to the collar ll.

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one member being supported by said brackets and the other member by saidstandard.

9. A sound reproducer for voice and musiccomprisingahousinghavinganopeninginone face thereof, a stifi vibratilediaphragm mounted in said housing and having one side exposed directlyto unconfined air through said Openin and having the other side exposedonly to air within said housing, said housing having an opening ofsubstantial area in back of said diaphragm and said opening beingcovered with a layer of sound-absorbing material and means forsupporting and driving said diaphragm, comprising an electromagneticunit.

10. A sound reproducer for voice and music comprising a housing havingan opening in one face thereof, a stiff conical diaphragm supported atits center and having one side exposed directly to unconfined air andhaving the other side exposed only to air within said hoiising, saidhousing having an opening of substantial area in back of said diaphragm,and said opening being covered by a sound filter, and means for drivingsaid diaphr m.

11. A sound reproducer for voice and music, comprising a housing havingan opening in one face thereof, a stifl, vibratile, conical diaphragmhaving its concave side exposed directly to unconfined air, and havingits convex side exposed only to air within said housing, said housinghaving an opening of substantial area in back of said diaphragm and saidopening being covered with a layer of sound-absorbing material, andmeans for supporting and driving said diaphragm comprising anelectromagnetic unit.

12. A sound reproducer for voice and music. comprising a housing havingan opening in one face thereof, a stiff vibratile, conical diaphragmhaving one side exposed directly to unconfined air through said openingand having the other side exposed only to air within said housing, saidhousing having an opening of substantial area in back of said diaphragmand said opening being covered with sound-absorbing material, and meansfor driving said diaphragm.

13. A sound reproducer for voice and music, comprising a housing havingan opening on one face thereof, a stiff, vibratile diaphragm mounted insaid housing. and having one side directly exposed to unconfined airthrough said opening, and having the other side exposedonly to airwithin said housing. said housing having an openingoi substantialareainback of said diaphragm and a sound filter interposed between saidopening of substantial area and saidvdiaphragm, and electromagneticmeans for driving said diaphragm.

14. A sound reproducer for voice and music comprising a housing havingan opening in-one face thereof, a still, vibratile diaphragm mounted'insaidhousingandhavingonesidecxpoeeddirectly to unconfined air throughsaid opening and having the other side exposed only to air within saidhousing, said housing having an opening of substantial areainbackofsaiddiaphragmand said opening being covered with a layer of felt iikematerial and electromagnetic means for driving said diaphragm.

15. A sound reproducer for voice and music, comprising a housing havingan opening in one face thereof, a stiff, vibratile, conical diaphragmmounted in said housing and having one side exposed directly tounconfined air through said opening, and having the other side exposedonly to air within said housing, said housing having an opening ofsubstantial area- 'in'back of said diaphragm and said opening beingcovered with a layer of sound-absorbing material, and electromagneticmeans tordriving said diaphragm' 16. A sound reproducer for voice andmusic, comprising a housing having an opening in one face thereof, astiff, vihratile diaphragm mounted in said housing and having one sideexposed directly to unconfined air through said opening, and having theother side exposed only to air within said housing, said housing havingan opening of substantial area in back of said diaphragm and saidopening being covered with a layer of soundabsorbing material soarranged that the sound radiated from the last-mentioned side of saiddiaphragm does not substantially exceed a small part of the soundradiated from said first side for most of the speech and music frequencyrange and electromagnetic means for driving said di- -Dhragm.

17. A sound reproducer for voice and music, comprising a housing havingan opening in one face thereof, a still, vibratile, conical diaphragmmounted in said housing and having its concave side exposed directly tounconfined air through said opening, and having its convex side exposedonly to air within said housing, said housing having an opening ofsubstantial area in back of said diaphragm and said opening beingcovered with a layer of sound-absorbing material so arranged as toabsorb a substantial amount of the sound radiated from said convex sideand an electromagnetic means for driving said diaphragm.

18. A sound reproducer for voice and music, comprising a housing havingan opening in one face thereof, a stiff, vibratile, conical diaphragm,mounted in said housing and having one side exposed directly tounconfined air through said opening and having its convex side exposedonly to air within said housing, said housing having an openingcommunicating with the rear of said diaphragm, said opening being ofsubstantial area and covered with'a layer of sound-absorbing'material soarranged as to absorb a substantial amount of the sound radiated fromsaid convex side and electromagnetic means for driving said diaphragm.

19. A sound reproducer for voice and music, comprising a housing havingan opening in one face thereof, a still, vibratile, conical diaphragmsupported at its center, and mounted within said housing and having itsconcave side exposed directly to unconfined air through said opening andhaving its convex side exposed only to air confined within said housing,said housing having an opening of substantial area communicatingwith'ths convex sideoi' said diaphragm andsaidopeningbeingcoveredwithalayerofsoundabsorbing material so arrangedas to absorb a substantial amount of the sound radiated from said convexside and electromagnetic means for driving said diaphragm.

20. A sound reproducer for voice and music,oomprisingacabinethavinganopeninginone wall thereof, a stiff vibratilediaphragm positioned within said cabinet at said opening in such manneras to have one side thereof exposed di-' rectly to unconfined air, andsaid cabinet having an opening behind said diaphragm. said opening beingcovered with a layer of sound absorbing material, and electromagneticmeans for driving said diaphragm.

21. A sound *reproducer for voice and music, comprising a cabinet havingan opening in one wall thereof, a still vibratile conical diaphragmpositioned within said cabinet at said opening and having one sidethereof exposed to unconiined air, said cabinet having an opening behindsaid diaphragm, said opening being covered with a layer of soundabsorbing material, means for preventing circulation of air from oneside of said diaphragm to the other within said cabinet, and means fordriving said diaphragm.

22. The combination of a support, a diaphragm, and a member connectedbetween said support and said diaphragm and provided with overlappingstaggered slots. l

28. The combination of a support, a diaphragm. and a member connectedbetween said support and said diaphragm and provided with overlappingstaggered slots substantially parallel with the periphery of saiddiaphragm.

24. In a support, a standard, a flexible member secured to andsurrounding said standard, said flexible member comprising a sheethaving openings hounded by curved edges therein and radially-extendingportions between said openings.

25. In a diaphragm support, a standard, a flexible member secured to andsurrounding said standard, said flexible member comprising a sheethaving arcuate openings therein, and narrow extending portions betweensaid openings.

26. In a diaphragm support, a standard, a flexible member secured to andsurrounding said standard, said flexible member comprising a sheethaving openings bounded by curved edges therein, and narrow extendingportions between said openings.

cones 27.1nasoundtranslatingin'stnunent.acasing having a front and rearopeningtherein, an acousticdiaphragmwithinthscasingandhavingoneofitssidesfscingsaidfrontopening,and a porous packing interposedbetween theothsr sideofthediaphragmandtheotheropeningin thecasing.

28. Inasmmdtranslatinginstrument,acasing having openings in oppositewalls, an acoustic diaphragm within the casing and having one ofitssidesfacingthe ii ninginoneofsaidwalls and a porous packinginterposed between the other side of the diaphragm and the other openingin the casing.

29. In a sound translating instrument, a casing having a front and rearopening, an acoustic diaphragm within the casing and having one of itssides facing one of said openings. and a sound iilter within said casingand interposed between the other side of said diaphragm and the other ofsaid openings.

30. An acoustic device comprising, in combination, a convex diaphragm, acylinder secured to said diaphragm on the convex side thereof, a voicecoil on said cylinder, and a flexible suspension secured thereto and toa support, said suspension being in the form of a multiplicity ofconcentric rings having radial connecting strips, and .said strips beingoffset outwardly.

31. In an electro-acoustic translating device, a magnetic structure, astiff conical diaphragm flexibly supported therefrom, a porous packingexposed to the atmosphere and surroundng the rear of said diaphragm outof contact therewith and shielding from sounds the side of the diaphragmtowards said magnetic structure.

32. In an electro-acoustic translating device, a magnetic structure, astiff conical diaphragm flexibiy supported therefrom, a porous packingexposed to the atmosphere and substantially entirely surroundingsaidmagnetic structure and shielding from sounds the side of thediaphragm towards said magnetic structure, and means for preventing saidpacking from contacting said diaphragm.

33. In a signal translating device, a conical diaphragm, an annularsupport adjacent the large end thereof, a support adjacent the small endthereof, and flexible connections between each of said supports and thediaphragm, and a coil entirely located at the small end of the cone.

CLINTON R.

